\NewDocumentCommand{\tangentcount}{ m }
 {
  \ellett_tangentcount:n { #1 }
 }
\cs_new:Npn \ellett_tangentcount:n #1
 {
  \int_case:nnn { #1 }
   {
    { 1 } { exactly ~ one }
    { 2 } { exactly ~ two }
   }
   { no }
 }
